Abstract: Objective: To understand the status of catastrophic health expenditure in poor urban families, analyze the influencing factors, and put forward the pertinence measures. Methods: 1100 families who received subsistence security in A City in Jilin Province were investigated by system sampling method with a self-designed questionnaire. The data analysis methods include chi square test, logistic regression model,etal. Results: The median of household expenditure on household health expenditure was 50%.Catastrophic health expenditure rate was 59.1%. The rate of proportion of self payment of cash expenditure on chronic disease for household cash health expenditure reached 0.9~1.0 was 33.5%.Influencing factors of catastrophic health expenditure for poor urban families were the highest cultural degree in family members, family members suffering from chronic diseases , hospitalization services utilization, awareness and utilization of medical assistance, family economic status. Conclusion: The household health expenditure and the rate of catastrophic health expenditure for poor urban families were very high. Chronic diseases gave great impacts on poor urban families. It was necessary to develop the medical assistance system, strengthen the community management of chronic diseases and improve the family economic conditions to reduce the catastrophic health expenditure.